Vitamin D and tissue citrate.

The increased elimination of urinary citrate effected by the administration of vitamin D (1) raises the question whether this is the result of a lowering of the renal threshold or a response to an increased accumulation in body tissues, or both. The reports in the literature on tissue citrate in this connection are limited and conflicting. While Freeman and Chang (2) and Harrison and Harrison (3) found an increase in serum citrate in the dog and the infant, respectively, when vitamin D was administered, Ochse (4) was unable to find any “significant” difference in the level of serum citrate in rachitic as compared with normal infants. Shock treatment with vitamin D actually reduced the citrate level. The wide distribution of citrate in the body (5, 6) and its high concentration in bone (7), as well as the large number of metabolic reactions in which citrate or its precursors participate (8), made it desirable to determine whether vitamin D could increase tissue citrate. In an ultimate analysis, such an effect could be the result of either its increased synthesis or its decreased destruction.